1. Field of the Invention
The present invention relates to an endoscope optics having a sealed outer tube in which a window is directly affixed to a distal end of the outer tube.
2. Description of Related Art
Endoscope optics of the aforementioned type are known in the state of the art, as shown in the German patent document 195 25 995 C1. The endoscope optics of this kind offer the substantial advantage of the window being directly affixed in the outer tube of which it covers the full cross-section and being perfectly sealed off for instance by soldering. Accordingly, the entire space inside the outer tube, which contains contamination-susceptible optical components and optical surfaces, is hermetically sealed. Such a design reliably secures the optics against invading liquids and vapors, which is particularly troublesome under the critical conditions of steam autoclaving to sterilize endoscope optics for medical applications.
However, optics of this kind, namely fitted with a window jointly covering the cross-sectional zone of the light guide and the image transmitter, incur the problem that the light radiates from the exit of the light guide into the distal entry end of the image transmitter. Such light radiation creates interfering light reflections in the image. As already discussed in the above cited document, light entering the window is reflected by the window and may be directed toward the light transmitter. As a result, the aforementioned German patent document assumes that direct light penetration from the light guide into the image transmitter no longer can take place in front of the window because direct light penetration is precluded by a partition.
Now it has been found that such an assumption is unwarranted. To a substantially interfering degree, light also passes through a gap between the distal edge of the partition and the window. Accordingly, the construction of the state of the art continues to suffer from unwanted light pollution created by light passing between the from the light guide into the image transmitter.
The present invention is directed toward precluding light penetration otherwise taking place already in front of the window.
The present invention is based on the insight that the known design of the above cited kind, wherein a partition internally and directly abuts the window, is unable to prevent light penetration inside this window. The partition and the outer tube undergo different thermal expansions. It must be borne in mind in this respect that endoscope optics of the above kind are subjected to high temperature fluctuations. When typically used in medical applications, temperature changes in the first place arise between room and body temperatures. During conventional steam sterilization, the optics is raised from room temperature to above 120xc2x0 C. and then is cooled to room temperature again. If the partition is designed to always abut the window in light-tight manner, then, in the presence of longitudinal thermal expansion, the partition will excessively stress the window and break it. If the partition""s length is selected so that it does not pressurize the window during such longitudinal thermal expansion, then a gap will necessarily exist between the partition distal wall and the window. Such a gap may transmit light.
Accordingly the present invention provides that the distal edge of the partition rests, by means of an elastic, light-tight insert, against the window. The insert assures optical sealing of the gap under all conditions of partition expansion, and this without unduly stressing said window. Accordingly the design of the present invention reliably prevents light from entering the image transmitter within the window, and removes the risk or danger of the window breaking. Tests have shown that as a result of the sealing operation of the insert, the essential portion of the interfering light penetration is precluded. An optics of the invention is applicable without suffering from significant light reflections. The invention also applies to all design variations and in particular, to endoscope optics with optic fiber cables as light guides and to image transmitters both in the form of optic fiber bundles and in the form of systems of relay lens elements. The partition may be configured at arbitrary cross-sections between the two cross-sectional zones, in particular in conventional manner as a system tube enclosing the image transmitter. Advantageously, the partition shall run not only across the range between the distal ends of light guide and image transmitter and the window, but also over the essential length of the light guide in order to avert also light penetration in a rear zone.
The spacer illustratively may be in the form of an adhesive connection of a material that was deposited as a liquid. However, in further accordance with the present invention, the spacer is an elongated, preferably flexible, body in the form of a loop, and thereby offers manufacturing and cost advantages resulting from such being separately or previously manufacturable.